For photovoltaic systems, electrical cables with a cable jacket made of crosslinked plastics are increasingly being used outdoors. These plastics are crosslinked chemically or by radiation, for example. Cables having a cable jacket made of crosslinked plastics are particularly robust and typically provide a longer service life outdoors than conventional cables with PVC jackets, e.g. against exposure to sunlight.
Typical warranty periods of photovoltaic modules are 20 years or more. Therefore, the cable assemblies and associated connectors that are employed should likewise have a correspondingly long service life. Hitherto, cable junctions have often been overmolded, optionally multiple times, and an adhesion promoter is used. Alternatively, a hollow plastic housing is used, which is then potted. Nevertheless, potted or overmolded cables junctions of cables that have a jacket of crosslinked plastics have the drawback that the crosslinked plastic material of the cable jacket typically does not form a good bond with the potting compound or overmolding compound. In other words, the potting compound or overmolding compound does not “stick” sufficiently to the cable jacket. As a result, there is a risk of ingress of water in the case of such junctions, which may have detrimental effects on the system. Similar difficulties may also arise with cable jackets made of plastics which, although not crosslinked, nevertheless do not form an adhesive bond with the potting compound or overmolding compound.
When being overmolded, the cable jacket is typically treated with an adhesion promoter, then the assembly is placed in an injection molding tool and the junction is overmolded. This is usually followed by another or several further overmolding processes. One reason for this is that large mass accumulations of the plastic mass should be avoided, which may lead to sink marks and increase the cycle time of the tool.
When being potted, a housing is typically used which encloses a cable branch junction, for example. Thereafter, the cavity is potted. The potting process takes a long time because the potting compound must cure first. Furthermore, additional components may be needed to help with strain relief and tightness. If strain relief of the cable is provided by the static friction of the potting compound on the wire insulation and the cable jacket, this does not seem to be optimal, not only for the aforementioned reasons.
Typically, high cable pull-out forces are required for photovoltaic cabling. Certain standards require resistance against cable pull-out forces of at least 156 N for inverter connectors, for example.
In Applicant's Sunclix® micon articles, clamps crimped onto the cable provide adequate strain relief. Nevertheless, this concept can be further developed in terms of cost and installation effort.